Jan 27, 2024 - Science

A tiny ant invasion wreaked havoc on lions in Kenya

Lions stalk prey under the cover of whistling-thorn trees.

Lions stalk prey under the cover of whistling-thorn trees. Photo: Victoria Zero

The invasion of big-headed ants set off a cascade of changes on the savanna in Kenya, seemingly even altering the diet of lions that live and hunt there, researchers reported Thursday.

The big picture: Mutualistic relationships between different species are the foundation of many ecosystems — savanna, coral reefs, seagrass beds and others.

  • "When you disrupt those mutualisms all kinds of crazy stuff can happen," says Todd Palmer, a professor of biology at the University of Florida and co-author of the paper that appeared today in the journal Science.

How it works: Native acacia ants form a body armor for whistling-thorn trees that dominate landscapes in East Africa, preventing elephants that pull entire trees out of the ground from feeding on them.

  • The trees are a source of food for rhinos and giraffes that nibble on their leaves; birds nest in them; and they pump nitrogen into the soil.
  • They're also important hiding places for lions as they hunt plains zebras.

When big-headed ants arrived and began to kill the acacia ants, the trees were exposed and elephants broke them at five to seven times the rate in areas that didn't have big-headed ants, the team reports.

  • A computer model of the field observations found that in places where the big-headed ants had invaded and lions no longer had cover as they hunted, zebra kills occurred nearly three times less.
  • But the density of lions didn't change, likely because they switched their prey to African buffalo, the researchers suggest.
  • "It was very surprising," says Douglas Kamaru, a graduate student at the University of Wyoming and lead author of the study.

Why it matters: "We think a lot about species conservation," Palmer says.

  • "But we don't think a lot about the conservation of interactions ... [that are] so crucial."
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